Simvastatin and parents

i am 55 and have been taking simvastatin for about 2 years although my cholestrol was under 5. over the last few months have had pain in my knees which i thought may be arthritis and then about 2 months ago the pain started in my left foot and became so severe that i had to change to an automatic car, still believing up until today that arthritis must be getting worse although my foot xray came back normal, i found this website today as my finger and thumb joints are hurting so much i cant hold anything and every muscle aching so much i just wanted to cry.after reading these letters i realize that even the choking feeling im sometimes getting isn't a menopausal panic attack and now i have checked my simvastatin leaflet an d box and realize that although my last cholesterol reading was only 3.5 one of my doctors has put my tablets up from 10 mg to 20 mg so big question is this an overdose ? im not taking another one of these pills an see what progress my health makes. i am slightly worried about heart disease and will look into herbal type as my parents use these,have never taken statins and are 90 and 87 so i think this speaks for itself,thanks everyone who has helped me diagnose my own illness!!!